Computer systems have become increasingly pervasive in our society. The processing capabilities of computers have increased the efficiency and productivity of workers in a wide spectrum of professions. As the costs of purchasing and owning a computer continues to drop, more and more consumers have been able to take advantage of newer and faster machines. Furthermore, many people enjoy the use of notebook computers because of the freedom. Mobile computers allow users to easily transport their data and work with them as they leave the office or travel. This scenario is quite familiar with marketing staff, corporate executives, and even students.
Furthermore, there is interest in the market for other types of computing devices. For instance, personal digital assistants, MP3 players, and cellular phones with calendar functions are growing in popularity. More and more of these devices have the capability to communicate together through wireless transmissions. For instance, many portable electronic devices are equipped with wireless transceivers adhering to wireless protocols such as the IEEE 802.11 standard or Bluetooth technology. A number of these devices can also connect to wireless local area networks (WLAN).
Given the popularity of such wireless devices, there are often times when a number of wireless transmissions are traveling through the area. These transmissions can interfere with each other and distort the signals. As a result, bad data packets or errors can occur. Current technology in some IEEE 802.11 (b) Wireless LAN access points provides a transmission speed step-down mechanism to improve signal range and resistance to noise. These access points evaluate the signal quality to a client by analyzing the packet error ratio (PER). If the PER is above a predefined threshold, the bit rate is successively dropped from 11 megabit/second (Mb/s) to 5.5 Mb/s, then to 2 Mb/s, and finally to 1 Mb/s if the PER does not improve over time. This mechanism allows clients with low signal to noise ratios due to a weak constant interfering source or a low received signal strength to receive transmissions at a reduced bit rate. However, this transmission rate step-down algorithm does not improve throughput if the interfering source is strong enough to block transmissions even at lower data rates.
The PER does not distinguish between a low noise environment and an environment having a sporadic noise source such as a Bluetooth device that corrupts packets only when the Bluetooth device and Wireless LAN devices are concurrently transmitting. In both cases, there is a random chance that a bit error will occur that is proportional to the ratio of the strength of the interfering noise to that of the desired signal. Thus at threshold regions, a packet error due to high noise can look the same as a packet error from sporadic noise. A packet error can be attributed to single bit error during the whole transition period.